1. Field of the Invention
This invention relates to character information separating apparatus for printed character reading systems. More particularly, the invention relates to improvements which ensure a highly accurate line-by-line separation of character information in the reading of the characters printed with a high line density or the characters printed with a closer line spacing on a source document.
2. Description of the Prior Art
With character readers known in the art, generally it has been the practice to read the characters on a source document, separate the thus read information line by line, successively dissect each of the lines into the individual characters from one end of the line and recognize each of the characters. As a result, it has been very important for each character to identify the line to which it belongs and thus it has been the practice with the conventional data sheets to leave a sufficient blank space between the lines. In other words, in accordance with the recommended standard character size I of the International Standard Organization (hereinafter simply referred to as an ISO) the character height is on the order of 2.8 mm and the usual practice is to print about three lines of characters per inch using for example a line spacing of about 5.7 mm. However, with the recent tendency toward extensive use of the character readers with various data processing systems, a need has arisen for increasing the line density and processing a large quantity of data in a short period of time so as to ensure the effective use of the character readers and a demand has begun to arise for increasing the line density up to about 6 lines/inch in the case of the previously mentioned size I.
However, if the line density is increased in this way, the characters of the adjacent two lines will tend to mingle with one another and even overlap one another in extreme cases, making it practically impossible for the conventional methods to effect the line-by-line separation of information and making the use of a character reader itself impossible. As a result, there is an absolute necessity for a printed character separating apparatus which is effective even in such a case.
A known line separating method which has been used widely will now be described. Firstly, the intended or object line is read and then the character information as a whole is projected in the line direction. The next step is to determine the center of the character area whose ends are surrounded by white background areas containing no character information and the separation of the intended line is accomplished on the basis of the thus determined center. In accordance with the previously mentioned recommended standard of the ISO, the tolerance for the vertical character misregistration (the vertical irregularity in the arrangements of the characters) is about 1/4 of a character for the adjacent line characters and about 1/2 of a character for the characters in the same line. As a result, if the density is as high as 6 lines/inch, there will be cases where the resulting linewise projection information contain no white background area and in such cases the line-by-line separation is of course impossible.
To overcome the foregoing deficiency, another method has been proposed in which the continuity of the white background conditions for the entire line is detected and used to accomplish the separation of the line. However, this known method tends to detect the continuous lines of the white background containing any lines other than the object line and result in a serious error. While this type of known method is effective in cases where the line spacing is considerably wide or the same type of characters such as numerals are in succession, the separation of lines is almost impossible in cases where the characters mingle with one another or any spaces or extraneous characters are included in the characters.